Weeds are one of the most challenging threats faced by agricultural lands and impart severe effect on crop yield thus impose a high cost to agriculture. The present study was made to characterize the weed communities associated with paddy fields of Mandakini valley, Uttarakhand. Field data was collected by quadrat method (size 1 m2) through field surveys in the year 2017-2018. A total of 57 weed species belonging to 45 genera and 19 families were recorded from the paddy fields. Echinochloa colona, Cyperus iria and Ageratum conyzoides are the most problematic weeds prevailing the paddy fields of the study area. The alpha diversity indices showed that Site 3 was the most diverse zone. High value of Sorenson index represented close similarity occurred in weed species in all the comparison between the sites. The Steinhaus coefficient demonstrated highest similarity intensity between Site 1 and Site 3.